5-Methyl-l,3-cyclopentadiene

The same anion is formed by loss of the most acidic proton from l-methyl-l,3-cyclo-pentadiene as from 5-methyl-l,3-cyclopentadiene. Explain. 

Similarly, 5-methyl-l,3-cyclopentadiene 24 rapidly rearranges at room temperature to yield a mixture of 1-methyl-, 2-methyl-, and 5-methyl-substituted products by... 

Because a [1,5] sigmatropic rearrangement involves three electron pairs (two IT bonds and one orbital-symmetry mles in Table 30.3 predict a suprafacial reaction. In fact, the [1,5] suprafacial shift of a hydrogen atom across two double bonds of a -ar system is one of the most conrmonly observed of all sigmatropic rearrangements. For example, 5-methyl-l,3-cyclopentadiene rapidly rearranges at room temperature to yield a mixmre of 1-methyl-, 2-methyl-, and 5-methyl-substituted products. 

A further utilisation of the Patemo-Buchi enone photoannulation reaction has been performed by Chaudhuri et al. ( ref 30 ) who, by employing 5-(trimethylsilyl)-l,3-cyclopentadiene 77 in acetonitrile at -50 °C ( see scheme 15 ), obtained in a regioselective way only the photoadduct 78, by reaction with methyl-diformyl acetate 48. 

Methyl-1,3-cyclopentadiene rearranges to give a mixture of 5-methyl-1,3-cyclopentadi-ene, l-methyl-l,3-cyclopentadiene, and 2-methyl-1,3-cyclopentadiene. Show how these products are formed. 

Upon UV irradiation in hydrocarbon solution, the hexacarbonyls of chromium, molybdenum, and tungsten react differently with conjugated dienes like 1,3-butadiene (la), ( )-l,3-pentadiene (lb), 2-methyl-1,3-butadiene (lc), ( , )-2,4-hexadiene (Id), ( )-2-methyl-l,3-pentadiene (le), 2-ethyl-1,3-butadiene (If), or 1,3-cyclohexadiene (Ig). Chromium hexacarbonyl (2) yields, with the acyclic dienes la-lf, tetracarbonyl-r/2-dienechromium(0) complexes (3a-3f) in a smooth reaction (8-10). With 1,3-cyclohexadiene, in addition to 3g, dicarbonylbis(>/4-l,3-cyclohexadiene)chromium(0) (4g) is obtained [Eqs. (7) and (8)j. During chromatography on silica gel, the 1,3-cyclohexadiene complex 3g dismutates readily to [Cr(CO)6] and 4g [Eq. (9)]. Under the same conditions with 2 1,3-cyclopentadiene (lh) yields, in a hydrogen-transfer reaction, the stable dicarbonyl- / 5-cyclopentadienyl-r/ 3-cyclopent-enylchromium (5) (11-13) [Eq. (10)]. 

Fig. 3.5. Relationship between log (retention time) and boiling point for a range of hydrocarbons on squalane at 43°C. A, aliphatics (and benzene) B, alicyclics, 1-4 = C5-Cg n-alkanes 5 = 2-methyl-butane 6 = 2-methylpentane 7 = 2,3-dimethylbutane 8-12 = C4-C8 1-olefins 13,15,17 = trans-(but-2-ene, pent-2-ene and hept-2-ene) 14,16,18 = e/s-(but-2-ene, pent-2-ene and hept-2-ene) 19 = 2-methylbut-l-ene 20 = 2-methylpent-l-ene 21 = 4-methylpent-l-ene 22 = 2-methylbut-2-ene 23 = cyclopentane 24 = cyclohexane 25 = methylcyclopentane 26 = methylcyclohexane 27 = cyclo-pentene 28 = cyclohexene 29 = 4-methylcyclohexane 30 = 1,3-butadiene 31, 32 = trans- and cis-1,3-pentadiene 33 = diallyl 34, 35 = trans- and c s-2-methyl-l,3-pentadiene 36 = cyclopentadiene ...

The total neutral essential oil from M. oleifera leaves is composed of 44 constituents and include toluene, 5-ter/-butyl-l,3-cyclopentadiene, benzaldehyde, 5-methyl-2-furaldehyde, benzeneacetaldehyde, linaloloxide, 2-ethyl-3,6-dimethylpyrazine, undecane, a-isophorone, benzylnitrile, 2,6,6-trimethyl-2-cyclohexane-l, 4-dione, 2,2,4-trimethyl-pentadiol, 2,3 -epoxycarane, p-menth-1 -en-8-ol, 2,6,6-trimethylcyclohexa-1,3 -dienecarbaldehyde, indole, tridecane, a-ionone, l,l,6-trimethyl-l,2-dihydronaphthalene, a-ionene, (1-damascenone, 3-ionone, ledene oxide, 2-ter/-butyl-l,4-dimethoxybenzene, ( )-6,10-dimethylundeca-5,9-dien-2-one, 4,6-dimethyl-dodecane, 3,3,5,6-... 

Other cyclopentadienes with reasonable C-H acidity, such as methyl indene-3-carboxylate (11) and l,5-dibenzoylcyclopenta-l,3-dienc (preferably existing in the 6-hydroxyfulvene form, 13), also successfully condensed with 2,3-dipropylcyclopropenone (10) when acetic anhydride was used as a dehydrating agent. ... 

Disubstituted cyclopropenes undergo addition to tetraarylcyclopentadienones to produce mixtures of exo- and emfo-adducts in which the endo-isomer predominates (Table 12).187188 The predominance of enr/o-product has been explained in terms of secondary orbital interactions, involving the methylene group of the cyclopropene.147 3-Methyl-3-vi-nylcyclopropene reacted with 2,3,4,5-tetraphenylcyclopenta-2,4-dien-l-one at the cyclopropene double bond and a [4+2] cycloadduct of unspecified stereochemistry was isolated (41% mp 231-234 °C) together with decarbonylated products reaction of 2-oxo-4,5-diphenyl-l,3-bis(methoxycarbonyl)cyclopentadiene with 3-methyl-3-vinylcyclopropene was more complicated and apparently attack occurred at both 71-bonds.1... 

Aliphatic C-5—C-6. Aliphatic feedstreams are typically composed of C-5 and C-6 paraffins, olefins, and diolefins, the main reactive components being piperylenes cis-[1574-41 -0] and /n j -l,3-pentadiene [2004-70-8f). Other main compounds iaclude substituted C-5 and C-6 olefins such as cyclopentene [142-29-OJ, 2-methyl-2-butene [513-35-9] and 2-methyl-2-pentene [625-27-4J. Isoprene and cyclopentadiene maybe present ia small to moderate quaatities (2—10%). Most steam cracking operatioas are desigaed to remove and purify isoprene from the C-5—C-6 fraction for applications ia mbbers and thermoplastic elastomers. Cyclopentadiene is typically dimerized to dicyclopentadiene (DCPD) and removed from C-5 olefin—diolefin feedstreams duriag fractionation (19). 

Cyclohexene-l,4-dione, 2,3,5-tiichloro-3, 6-bis(l,l-dimethylethyl)- [5-Cyclo-hexcne-1,4-dione, 2,3,5-tnchloio-3,6-dwert-butyl-], 55, 33 Cyclopentadiene, 55, 15,16 Cyclopentane acetyl-,55,25 Cyclopentane 1-cyano-l-phenyl-, 55,94 Cyclopentane methyl-, 55, 62 Cyclopropane, 1-acetyl-l-phenyl-, 55 94... 

The photo-induced exo selectivity was observed in other classic Diels-Alder reactions. Data relating to some exo adducts obtained by reacting cyclopentadiene or cyclohexadiene with 2-methyl-1,4-benzoquinone, 5-hydroxynaphtho-quinone, 4-cyclopentene-l,3-dione and maleic anhydride are given in Scheme 4.13. The presence and amount of EtsN plays a decisive role in reversing the endo selectivity. The possibility that the prevalence of exo adduct is due to isomerization of endo adduct under photolytic conditions was rejected by control experiments, at least for less reactive dienophiles. 

MACROCYCLIC POLY AMINES, 58, 86, 90 MACROLIDES, 58, 98 Magnesium, bromo phenyl, 58, 138 Magnesium methyl carbonate, 56, 121 Maleic acid, methyl ester, 56, 63 Manganese, tricarbonyl[(l,2,3,4,5-7))-l-carboxy-2,4-cyclopentadien 1 yl], ... 

C4H 2OSi, Silane, methoxytrimethyl-, 26 44 CH4N, Propane, 2-isocyant-2-methyl-ruthenium complex, 26 275 C][l,4]-dithiin-2-thione, 26 389 CHfc, 1,3-Cyclopentadiene cobalt complex, 26 191-197, 309 chromium, molybdenum, and tungsten complexes, 26 343 iron complex, 26 232-241 mercury-molybdenum-ruthenium complex, 26 333... 

Asymmetric hydrosilylation of cyclopentadiene with HSiCl3 catalyzed by a Pd complex of (Sj-f/ -ferrocenylphosphine (240, Rf = C3F7) proceeds in a 1,4-manner to give 3-silyl-1-cyclopentene (239, X = Cl) with up to 60% ee (R) (equation 93)246. The same reaction using (5,)-2-(A-methanesulfonylamino)-3-methyl-l-diphenylphosphinobutane (241) and HSiMeCF yields 239 (X = Me) with up to 71% ee (S) (equation 93)245. In a similar manner, the reaction of 1,3-cyclohexadiene with HSiF2Ph catalyzed by (/ )-(5 )-l-diphenylphosphino-2-(l-acetoxyethyl)ferrocene (PPF-OAc) affords (,S )-3-silyl-l-cyclohexene (242) with 77% ee (equation 94)247. 

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